The present invention relates to a method of adhering polishing pads of a polishing apparatus, which is capable of simultaneously polishing both side faces of a work piece, and a suitable jig for the method.
In a polishing apparatus capable of simultaneously polishing both side faces of a work piece, e.g., wafer, a carrier holding the work piece is rotated between a lower polishing plate and an upper polishing plate, which are independently rotated, so that the both side faces of the work piece can be simultaneously polished by polishing pads, which are respectively adhered on the upper and the lower polishing plates.
A mechanism for rotating carriers is shown in FIG. 7. In FIG. 7, a plurality of carriers 208 are engaged with an internal gear 204 and a sun gear 206, which is located at the center of the internal gear 204.
Gear teeth are formed in an outer circumferential face of each of the disk-shaped carriers 208. The gear teeth engage with inner gear teeth of the internal gear 204 and outer gear teeth of the sun gear 206, so that each of the carriers 208 is rotated and moved around the sun gear 206.
A plurality of the carriers 208 are provided between the internal gear 204 and the sun gear 206, and each of the carriers 208 has a plurality of through-holes 207, in each of which the work piece to be polished is held. With this structure, a plurality of work pieces can be simultaneously polished. An example of such polishing apparatus is disclosed in Japanese Patent Gazette No. 9-239657.
Note that, in the polishing apparatus disclosed in the Japanese gazette, inner pin gears act as the sun gear, and outer pin gears act as the internal gear.
In the above described polishing apparatus, the polishing pads, which are respectively adhered on the upper and lower polishing plates, must be periodically exchanged. A method and an apparatus for adhering polishing pads is disclosed in Japanese Patent Gazette No. 59-53151. In the method, the polishing pads are adhered by the steps of: tentatively adhering the polishing pads on polishing faces of an upper and lower polishing plates; clamping a roller, which is rotatably held, between the upper and lower polishing plates; and rotating the upper and lower polishing plates in the opposite directions so as to fully adhere the polishing faces of the polishing plates.
In a large polishing plate, on which the polishing pad is adhered, circumferential velocities of an inner part of the polishing plate and an outer part thereof are clearly different. If the polishing plate is small, the velocity difference can be ignored for exchanging the polishing pad. However, these days, large polishing plates have been required. Therefore, the velocity difference between the inner part and the outer part of the large polishing plate cannot be ignored. In some cases, the roller bites the polishing pad, especially an inner part of the polishing pad is apt to be damaged.